The present invention relates to a mirror installation in an optical device, and more particularly to the installation structure and the installation method of a reflection mirror in a light scanning device.
In the prior arts, one of well known is a laser beam scanning device employed in, for instance, a laser printer. In the laser scanning device, a deflecting means is provided for scanning a predetermined area with a laser beam which is emitted, for example, from a fixed semiconductor laser.
The deflecting means has at least one deflecting surface which is perpendicular to a light passage of the laser beam emitted from the laser. The deflecting means is controlled to change an angle of its deflection surface with respect to the emitted laser beam so that a relative reflection angle against the emitted laser beam can be continuously changed.
In the laser printer employing the above scanning device, it is necessary to synchronize the modulation of the laser beam with its scanning operation, and so a photo-sensor is usually arranged at an edge zone of the beam scanning area to take timing of the beam modulation.
The photo-sensor is, however, often located at a position which is out of the beam scanning area due to requirements for effective arrangements of related parts and so on, and a reflecting mirror is instead placed at the edge zone of the beam scanning area for directing the beam to the out-placed photo-sensor.
The mirror has conventionally been installed in the device, for example, by means of a leaf spring 9 and a tapping screw 10 as illustrated in FIG. 7, wherein reference numerals 7c and 8 indicate a reflecting mirror and a mounting wall formed on a housing case 2,. respectively.
With this installation, the rear side surface of the reflection mirror 7c first abuts the installation wall 8 and then urged and fixed thereto by the leaf spring 9 and the tapping screw 10. Accordingly, installing work is troublesome and time-consuming. Further, mirror surface would incline due to roughness of the rear surface of the mirror and/or to uneven thickness of the mirror, which influences timing of the modulation of the laser beam.